Carmelo Anthony could only watch in bewilderment. Metta World Peace stripped the ball from him at midcourt during the Knicks’ intrasquad scrimmage Sunday at Columbia University, chased after the loose ball and finished with a fast-break slam dunk. The packed crowd at Levien Gymnasium howled. Anthony shook his head.

It wasn’t a good feeling, but Anthony will be better for it. Anthony is facing a defensive beast in practice every day of training camp. How can he not be better for it?

World Peace’s value will be seen on many levels this season and his goal is to make sure Anthony is the Knicks’ “leading guy.’’

“It’s more about we got to make each other better,’’ said World Peace, who ironically donned Anthony’s No. 7 practice jersey. “We don’t want to come out here and kill each other, especially in front of the media and fans. That’s not what we’re here for. This is what we do in practice.

“Melo had great days in practice, but we try to go at it. It’s the only way we can get better. If we push each other, try to make it hard on him, so when we get out on the floor [in a game], it’ll be easy and he can be the leader in scoring and be the leading guy. I want Melo to be the leading guy. But we got to do that together.”

Anthony was not made available to reporters after practice, but J.R. Smith said he sees the new practice challenge facing last season’s NBA leading scorer. It’s different than Anthony being guarded by Chris Copeland last season.

“Just to see Metta guard Melo in practice, it’s the first time I’ve seen him in the years we’ve been together, get a real challenge for him almost every day,’’ said Smith, who also was Anthony’s teammate with the Nuggets. “Melo’s taking it head on. Defense is what we preach and [taking] pride in on our team. Hopefully Metta keeps doing what he’s doing and gets guys into it.’’

World Peace hit two more 3-pointers during the scrimmage — his perimeter shooting continuing to look very smooth in training camp. Cut by the Lakers via the amnesty rule, the former Ron Artest, 33, does not look done yet. He sprained his ankle in practice last week and the Knicks had to beg him not to make the trip to Baltimore.

“I’m impressed with everything [World Peace has] done,’’ Knicks coach Mike Woodson said. “I’m going to be honest with you. He’s a guy we had to make take days off and take a game from him. He was there early. He’s go, go, go. I like that. He’s a tough kid. There’s nothing he can‘t do on the basketball court.

“All those things are great when you’re talking about trying to win at a high level. He does all the little things to help you win as well. I can’t wait to really get started when it counts and he’ll be a big part of what we do.’’

Lakers coach Mike D’Antoni gave former Knicks general manager Glen Grunwald rave reviews on World Peace in July after the Lakers cut him for financial purposes. D’Antoni was most impressed World Peace took just two weeks to heal from midseason knee surgery last season — an example of grit and dedication.

“You can’t be less than what you are,’’ World Peace said, explaining his longevity. “Be you. I work hard. I work on my body, try to stay in shape. I let people call me old. I can’t help I’m 33. God put us in this world and you’ll age. Nothing I can do about that. But what I can do is I can continue to work hard and stay in shape and I’m moving pretty well.’’

He also wants to mold the youthful batch of Knicks — not just Anthony.

“I want to help the young guys,’’ World Peace said. “Because in the playoffs, we’re going to need everybody. Not 100 percent intelligent, but [have them] at their peak intelligence in the playoffs, bringing the best they can bring mentally.’’